This invention relates to a high voltage supply current stabilizing circuit for stabilizing constant currents which, in an image recording apparatus, are supplied to the charging unit and the peeling unit from the high voltage source.
A high voltage supply current stabilizing circuit has been employed in an image recording device. In the image recording apparatus, as shown in FIG. 3, a photo-sensitive material 12 is charged with a charging unit 11, to which a constant current is supplied from a high voltage source (not shown), and the output laser beam of a laser oscillating section 13 is applied to the photo-sensitive material 12 thus charged to form a latent image therein. Thereafter, the toner 15 in a developing section 14 is applied to the latent image thus formed, to develop it into a toner image. The toner image is transferred onto a recording sheet 17 with a transferring unit 16, which is conveyed into the apparatus. Upon completion of the transferring of the toner image, a peeling unit 18, to which the high voltage source supplies a constant current, operates to discharge the recording sheet 17 thereby to peel the recording sheet 17 from the photo-sensitive material 12. Thereafter, the recording sheet is ejected from the apparatus.
FIG. 4 shows the high voltage supply current stabilizing circuit for supplying the constant currents from the high voltage source to the charging unit 11 and the peeling unit 18. In FIG. 4, the charging unit 11 and the peeling unit 18 are represented equivalently by load resistors R1 and R3, respectively. The output constant current I of the high voltage source is divided into two constant currents I-i and i. The constant current I-i is supplied to the load resistor R1, and the constant current i is supplied through a current stabilizing resistor R2 to the load resistor R3. The relation between the resistors and the currents are: EQU (R2+R3)i=R1(I-i) =R1I-R1i (1)
From equation (1), the current i is: EQU i=R1I/(R1+R2+R3) (2)
If it is assumed that the resistances of the load resistors R1 and R3 are 14.4 M.OMEGA. and 50 M.OMEGA., respectively, the value of the constant current I is 285 .mu.A, and the resistance of the resistor R2 is 50 M.OMEGA., then, according to equation (2) the current i is: ##EQU1##
However, if the current to the peeling unit 18 becomes higher for instance because of the installation error of the charging unit 16 and the peeling unit 18 (the distance between the two units being reduced), then it may be difficult to satisfactorily transfer the toner image onto the recording sheet 17. Alternatively, if the resistance of the peeling unit 18 is higher because of variations in environmental condition (such as temperature and humidity) of the peeling unit 18 or when the latter is made dirty; more specifically, if the resistance R3 is doubled to 100 M.OMEGA., then according to equation (2) the value of the current i of the peeling unit 18 is decreased to 25 .mu.A, 69.7% of the above-described value. As a result, it becomes rather difficult to smoothly peel the recording sheet 17 off the photo-sensitive material, and a toner explosion may take place.